RU2748537C1 - Method for producing oxide-silicon carbide cutting ceramics of new fraction - Google Patents

Abstract

FIELD: powder metallurgy.

SUBSTANCE: invention relates to powder metallurgy, in particular to the manufacture of high-strength cutting plates from oxide-silicon carbide ceramics. It can be used to equip cutting tools for processing difficult-to-cut steels and materials on metalworking machines. Silicon dioxide is calcined at a temperature of 1650−1750°С, subjected to fine vibration grinding on a vibrating machine for 2.5-3.0 hours and dried. After drying, mix 60% silicon dioxide, 3% zirconium carbide, 30% titanium carbide, 5% tungsten carbide and 2% nitrogen in liquid until uniform distribution over the volume and the formation of a suspension, which, after introducing binders into it, is subjected to spray drying to obtain a mixture. A cutting plate is pressed from the mixture obtained, sintering is carried out at a temperature of 3900-3950°С and short-term annealing with an exposure of 10.0-15.0 minutes at a temperature of 1600-1650°С, and the sintered plate is machined to obtain a roughness of the edges equal to 0, 08-0.16 microns.

EFFECT: increased intergranular corrosion resistance, wear resistance, plasticity, impact strength and resistance of cutting inserts when processing difficult-to-machine steels.

1 cl

Description

The invention relates to the manufacture of high-strength ceramic plates for equipping cutting tools for processing difficult-to-machine steels and materials on metalworking machines.

Known and produced in the Russian Federation [GOSTs for cutting ceramics VOK-60 GOST 25003-81; VOK-71 GOST19043-80; In addition to GOSTs, Handbook, ed. Zhed V.P. Cutting tools equipped with superhard and ceramic materials and their use: a reference book / V.P. Zhezh [and others]. - Moscow; Mechanical engineering, 1987. - 319 p.]

A known method of producing a ceramic plate for cutting tools [Patent RU No. 2699434, IPC C22C 29/12, B22F 3/16, B23B 27/14, publ. 09/05/2019], including the calcination of alumina containing α-A1 ₂ O ₃ and γ-A1 ₂ O ₃ , its vibration grinding, enrichment, drying to obtain aluminum oxide modification α-Al ₂ O ₃ , its mixing with silicon oxide, titanium carbide , tungsten carbide, boron carbide, chromium oxide, nickel, molybdenum, niobium and cobalt, plasticization and hot pressing to obtain a pressed plate, sintering, annealing with exposure for 5-10 minutes in the temperature maximum and its mechanical processing. Improvement of the physical and mechanical characteristics of the ceramic insert for the cutting tool is provided.

A known method of producing a ceramic plate for cutting tools [Patent RU No. 2679264, IPC B23B 27/14, B22F 3/15, C22C 29/12, publ. 02/06/2019], including the calcination of alumina, its vibration grinding, beneficiation, drying to obtain alumina modification α-Al ₂ O ₃ . The obtained aluminum oxide is mixed with alloying components at the following ratio of components, wt%: aluminum oxide 58-60, titanium carbide 30-32, chromium oxide 5-7, nickel 2-3, molybdenum 1-2. Further, plasticization and hot pressing are carried out to obtain a pressed plate, sintering and annealing with a holding time of 5-10 minutes in the region of the temperature maximum of the obtained plate and its mechanical processing. The invention provides an increase in the resistance of the obtained ceramic plates when processing difficult-to-machine materials up to 35-40 minutes, the hardness and strength in bending up to 990 MPa.

In addition, reference books:

Mes'kin V.S., Fundamentals of steel alloying, Ed. second, revised and add. Moscow: Metallurgy, 1964 .-- 684 p.

Puchkin V.N., Kornienko V.G., Litvinov A.E. Skhirtladze A.G. Physicochemical study of cutting ceramics during machining of difficult-to-machine steels on CNC machines (methodology). Monograph Ed. FSBEI HE "KubSTU", Krasnodar. 2016. Oxide-carbide grades VOK-60, VOK-63, VOK-73 (mixed, "metallic", "black") ceramics, consisting of oxide A1 ₂ O ₃ (up to 60%), TiC (up to 20 - 40% ), ZrO ₂ (up to 20 - 40%) and other carbides of refractory metals with some alloying additions. Oxide-carbide ceramic plates are produced by hot pressing in graphite molds. The process is more laborious than the process of producing oxide ceramics. Plates are used for machining malleable, bleached cast irons, heat-treated, case-hardened and hardened steels with a hardness of HRC 30 - 65.

As the main raw material, aluminum oxide powder Al ₂ O ₃ (up to 60%), TiC (up to 20 - 40%), ZrO ₂ (up to 20 - 40%) and other carbides of refractory metals with some alloying additions are used. Oxide-carbide ceramic plates are produced by hot pressing in graphite molds. The process is more laborious than the process of producing oxide ceramics. Plates are used for machining malleable, bleached cast irons, heat-treated, case-hardened and hardened steels with a hardness of HRC 30 ... 65.

The manufacture of plates begins with grinding the components of the mixture and preparing the charge. Then the components are mixed, the prepared mixture is wet milled, dried, dosing and hot pressing. Having finished pressing, the mold is disassembled, the pressed blanks are taken out and transferred to mechanical processing.

The quality and stability of cutting inserts is largely determined by the following factors: the content of titanium carbide and aluminum oxide in the initial charge, the grinding time of the mixture, the temperature and holding time during hot pressing, and the pressing pressure.

The hardness of the plates at the time of delivery is HRA 92-94.

The durability of plates at the stage of delivery when cutting difficult-to-machine and heat-resistant steels of 12Х18Н10Т, 14Х17Н2, etc. - 60 min.

Mechanical properties of plates at the stage of delivery: bending stress = 600 MPa; density 4.2 g / cm ³ ; grain size 2 ... 3 microns; hardness HRA 94.

The disadvantages of oxide-carbide cutting ceramics (RC) based on aluminum oxide are fragility, low wear resistance and corrosion resistance, temperature resistance, and resistance when processing difficult-to-machine steels and materials.

The closest in technical characteristics to the prototype of the proposed OKRK-60 are plates made of oxide-carbide cutting ceramics brands VOK-60, VOK-63, etc., produced by our domestic industry VOK-60 GOST 25003-81 [http: //docs.cntd. ru / document / 1200009570]; VOK-71 GOST19043-80 [http://docs.cntd.ru/document/1200009409].

Oxide-carbide (mixed, "metallic", "black") ceramics, consisting of oxide A1 ₂ O ₃ (up to 60%), TiC (up to 20 - 40%), ZrO ₂ (up to 20 - 40%) and other carbides refractory metals with some alloying additions. Oxide-carbide ceramic plates are produced by hot pressing in graphite molds. The process is more laborious than the process of producing oxide ceramics. Plates are used for machining malleable, bleached cast irons, heat-treated, case-hardened and hardened steels with a hardness of HRC 30 - 65.

The most famous brands of ceramics of this group are domestic VOK-60 and foreign SHT-1, SH-1, SH-20 ("Feldmülle"), NS-2 ("Nippon Technical Ceramic"), NRS-A2 ("Toshiba Tungaloy") , CC650 (Sandvik Koromant, Sweden), etc.

The disadvantages of oxide-carbide RK based on aluminum oxide are: fragility, low wear resistance and corrosion resistance, temperature resistance, and resistance when processing difficult-to-machine steels and materials.

The production of inserts from cutting ceramics based on aluminum oxide does not require the use of scarce materials, as well as unique or non-standard technological equipment.

As the main raw material, aluminum oxide powder Al ₂ O ₃ (up to 60%), TiC (up to 20 - 40%), ZrO ₂ (up to 20 - 40%) and other carbides of refractory metals with some alloying additions are used. Oxide-carbide ceramic plates are produced by hot pressing in graphite molds. The process is more laborious than the process of producing oxide ceramics. Plates are used for machining malleable, bleached cast irons, heat-treated, case-hardened and hardened steels with a hardness of HRC 30 - 65.

The technical result of the invention is:

- increase in intergranular corrosion resistance, temperature wear resistance, plasticity, impact strength and performance of plates made of oxide-silicon carbide cutting ceramics OKRK-60;

- increasing the yield point during hot pressing and sintering of plates;

- increasing the strength and hardness of the plates;

- improvement of physical and chemical properties of physical: - plasticity, impact strength, strength, density; average grain diameter, chemical: with the introduction of SiO ₂ ≥ 60% into the main fraction, the following chemical compounds - ZrC ≥ 3%; TiC ≥ 30%; WC ≥ 5%; N ≥ 2%, which contribute to the formation of hardening phases, dissolution of austenite, increase the hardness and resistance to tempering, high temperature strength and corrosion resistance, as well as facilitate sintering and inhibit the growth of grains up to 60% Si oxide-silicon carbide cutting ceramics of the new chemical composition OKRK-60;

- increasing the durability of plates made of oxide-silicon carbide cutting ceramics of a new chemical composition OKRK-60, when cutting difficult-to-machine, heat-resistant, austenitic steels 12X18H10T, 40X13, 14X17H2, etc .;

- establishment of temperature regimes for cutting when machining difficult-to-machine austenitic steels 12X18H10T, 40X13, 14X17H2, etc., as well as thermodynamic laws and modes of this process, which increases the temperature interval in the cutting zone of the tool-workpiece to 600 ° C when cutting difficult-to-machine steels and materials as a result how the cutting properties of the cutting tool equipped with plates of cutting ceramics of a new fraction and the safety of the plate itself at the set cutting temperatures are preserved;

- determination of rational cutting conditions, in which the wear resistance of the cutting tool equipped with plates of oxide-silicon carbide cutting ceramics of a new chemical composition OKRK-60, when processing difficult-to-machine, heat-resistant, austenitic steels using new cutting fluids with additives according to the KubGTU patent No. 2101333 with the following mass composition: formic acid 12 ... 13%; maleic acid 8 ... 9%; fumaric acid 7 ... 8%; succinic acid 8 ... 9%; furanones 35 ... 36%, the rest - water, will be maximum.

Rational cutting conditions when processing hard-to-machine, heat-resistant, austenitic steels were taken as a result of testing the speed V = 97 ... 110 m / min; feed S = 0.07 ... 0.097 mm / rev; cutting depth t = 0.1 ... 0.5 mm. With the established rational cutting conditions, the durability of the cutting tool equipped with plates of cutting ceramics of a new fraction is maximum and reaches up to T = 180 min.

The technical result is achieved due to the fact that according to the method of manufacturing oxide-silicon carbide cutting ceramics of a new fraction, chemical compounds ZrC are added to the main fraction of silicon dioxide using a dispenser and an analytical balance; TiC; WC and nitrogen in a liquid state are thoroughly mixed until the mass is evenly distributed throughout the volume and an aqueous suspension is formed, which, after the introduction of binders, is spray-dried, then the technological process of preparation is interrupted, and the resulting mass is monitored for chemical purity, workability, density, average diameter grains, which must correspond to the arithmetic mean value not exceeding 1.5 microns, then the cutting plates are pressed, followed by hot sintering, additionally silicon oxide is calcined to a temperature of 1700-1750 ° C and is subjected to fine vibration grinding on a vibrating unit for 2.5-3, 0 h, the resulting mass is enriched and dried, the resulting masses are mixed, the plates are plasticized and hot pressed from the resulting mixture, the density of sintering of the plates and the grain size of the plates are monitored, in conclusion, the plates are machined to obtain the roughness of the edges Ra = 0.08-0, 16 μm, with The pressed plates are sintered at a temperature of 3900-3950 ° C and a short-term annealing mode with an exposure of 10.0-15.0 min at a temperature of = 1600-1650 ° C, and the percentage of the chemical compound is as follows:

silicon oxide ≥ 60%,

zirconium carbide ≥ 3%,

titanium carbide ≥ 30%,

tungsten carbide ≥ 5%,

nitrogen ≥ 2%.

Here are the characteristics of the chemical components.

– 908,3 кДж × моль^-1, стандартная молярная энергия Гиббса образования

= -854,2 кДж × моль^-1, молярная энтальпия плавления

кДж × моль^-1 не растворяется в Н₂О (в воде).SiO ₂ ≥ 60%; (silicon oxide) - molecular weight M = 60.08; B / c, density ρ = 2.32 g / cm ² ; melting temperature t _pl = 1730 ° C; phase displacement temperature α → β , 242 ° С, standard molar heat capacity С0 _p = 44.18 J × mol ^-1 × K ^-1 , standard molar entropy S0 = 42.7 J × mol ^-1 × K ^-1 , standard molar enthalpy of formation

- 908.3 kJ × mol ^-1 , standard Gibbs molar energy of formation

= -854.2 kJ × mol ^-1 , molar enthalpy of melting

kJ × mol ^-1 does not dissolve in H ₂ O (in water).

– 206,7 кДж × моль^-1, стандартная молярная энергия Гиббса образования

= -197,4 кДж

моль^-1, не растворяется в Н₂О (в воде).ZrC ≥ 3%; (zirconium carbide) - molecular weight M = 103.23; dark gray, shiny color, density ρ = 6.7 g / cm ² ; melting temperature tmelt ≈3500 ° С; boiling point tboil ≈ 5100 ° С, standard molar heat capacity С0 _p = 37.90 J × mol ^-1 × K ^-1 , standard molar entropy S0 = 33.3 J × mol ^-1 × K ^-1 , standard molar enthalpy of formation

- 206.7 kJ × mol ^-1 , standard Gibbs molar energy of formation

= -197.4 kJ

mol ^-1 , does not dissolve in H ₂ O (in water).

– 209 кДж × моль^-1, стандартная молярная энергия Гиббса образования

= -205,7 кДж × моль^-1, не растворяется в Н₂О (в воде) и в кислотах HCl. H₂SO₄, реагирует с HNO₃ + HF, расплавляется щёлочью.TiC ≥ 30% (titanium carbide) - molecular weight M = 59.91; gray color, density ρ = 4.92 g / cm ² ; melting temperature tmelt ≈ 3140 ° С; boiling point tboil ≈ 4300 ° С, standard molar heat capacity С0 _р = 34.30 J × mol-1 × K ^-1 , standard molar entropy S0 = 24.7 J × mol-1 × K ^-1 , standard molar enthalpy of formation

- 209 kJ × mol ^-1 , standard Gibbs molar energy of formation

= -205.7 kJ × mol ^-1 , does not dissolve in H ₂ O (in water) and in HCl acids. H ₂ SO ₄ , reacts with HNO ₃ + HF, melted with alkali.

– 41 кДж × моль^-1, стандартная молярная энергия Гиббса образования

= -39,5 кДж × моль^-1, не растворяется в Н₂О (в воде). WC ≥ 5% (tungsten carbide) - molecular weight M = 195.86; gray-blue color, density ρ = 15.7 g / cm ² ; melting point tmelt = 2600 ° C; standard molar heat capacity С0р = 35.10 J × mol ^-1 × K ^-1 , standard molar entropy S0 = 35 J × mol ^-1 × K ^-1 , standard molar enthalpy of formation

- 41 kJ × mol ^-1 , standard Gibbs molar energy of formation

= -39.5 kJ × mol ^-1 , does not dissolve in H ₂ O (in water).

0 кДж × моль^-1, стандартная молярная энергия Гиббса образования

= 0 кДж × моль^-1, молярная энтальпия испарения

5,59 кДж × моль^-1, показатель преломления n = 1,00052825.N ≥ 2%; - nitrogen, molecular weight M = 28.01 g / l; colorless. gas or liquid, density ρ = 1.2506 G / cm ² ; liquid p = 0.808-196 G / l, melting point tmelt = -210 ° C; boiling point tboil = - 195.8 ° С, critical temperature tcr = -149.90 ° С, critical pressure ркр = 3.906 MPa for gas, ркр = 0.304 MPa for liquid, standard molar heat capacity С0р = 29.10 J × mol ^{- 1} × K ^-1 , standard molar entropy S0 = 199.9 J × mol ^-1 × K ^-1 , standard molar enthalpy of formation

0 kJ × mol ^-1 , standard Gibbs molar energy of formation

= 0 kJ × mol ^-1 , molar enthalpy of vaporization

5.59 kJ × mol ^-1 , refractive index n = 1.00052825.

Isp. letter: V.A. Rabinovich, Z. Ya. Havin. A short chemical reference book. Ed. 3rd, Revised and add. Under the general editorship of Doctor of Chemical Sciences A.A. Potekhinai Ph.D. A.I. Efimova. Leningrad "Chemistry" Leningrad branch 1991. - 432 p.

Let's consider an example of making plates.

The production of plates from oxide-silicon cutting ceramics of a new chemical composition grade OKRK-60 for equipping the cutting tool consists of the following methods and operations:

Raw materials for the manufacture of plates from oxide-silicon carbide cutting ceramics of a new chemical composition grade OKRK-60 are tested according to the following technology, which determines:

- chemical purity (contamination of alumina with compounds Na ₂ O, CaO is unacceptable);

- humidity;

- the surface area of the grains, which characterizes the activity of the material during sintering and allows the estimated grain size to be estimated;

- compressibility (determined by the conditions for processing alumina);

- control of the sintering density of the plates;

- control of the grain size of the plates.

Next, the charge is prepared.

We add SiO to the main fraction using a batcher and an analytical balance₂ 60%, in percentage content small amounts of chemical compounds WC 5%, ZrC 3%; TiC 30% and nitrogen N 2%; which contribute to the formation of strengthening phases, increase the hardness and resistance to tempering, heat resistance and corrosion resistance, impact strength, plasticity of plates, as well as facilitating sintering and inhibiting grain growth. When this "mass" is thoroughly mixed in a mixer, these additives are evenly distributed throughout the volume; an aqueous suspension is obtained, which, after the addition of binders, is subjected to spray drying. Then the technological process of preparation is interrupted, and the resulting mass is controlled: chemical purity; workability; density; the average diameter of the grains, which must correspond to the arithmetic mean value not exceeding 1.5 microns.

After control, with positive results, you can proceed to pressing the cutting inserts and subsequent hot sintering.

Silicon oxide SiO _{2 is} calcined up to 1650-1750 ° C and is subjected to fine vibration grinding on a vibrating unit for 2.5-3.0 hours to obtain particles with a size of 0.8 ... 1.5 microns (up to 90 ... 95% in the bulk) at the maximum particle size is 2 microns. The resulting mass is enriched and dried.

If we go beyond the specified rational temperatures of 1650-1750 ° C, there will be a change in the crystal structure of the plates, the growth of grains in the alloy will occur, which will lead during testing to plate chipping, cracks and plate brittleness and dullness, when cutting difficult-to-machine steels, as well as sticking molten metal onto the work piece, which degrades the quality and accuracy of the work piece. At the same time, the durability of the cutting tool equipped with plates made of cutting ceramics of the new OKRK-60 fraction decreases.

In the bulk of the dry powder of silicon oxide (SiO ₂ ≥ 60%), we introduce chemical compounds in the following proportion: WC ≥ 5%, ZrC ≥ 3%; TiC ≥ 30% and nitrogen N ≥ 2%. Then the plates are plasticized and hot pressed from the resulting mixture.

Pressed plates are sintered from oxide-silicon carbide cutting ceramics grade OKRK-60, at a temperature of 3850-3900 ° C and a short-term annealing mode with an exposure of 10.0-15.0 min at a temperature of 1600-1650 ° C.

Due to the fact that the indicated melting and boiling points are high of chemical compounds (carbides) in solution, rational temperature conditions were applied when pressing and sintering plates

The sintering density of the plates and the control of the grain size of the plates are monitored.

In conclusion, the plates are machined to obtain the roughness of the edges Ra = 0.08-0.16 microns.

As a result of the development and manufacture of high-strength inserts from oxide-silicon carbide cutting ceramics of a new chemical composition, the following result is achieved for equipping the cutting tool:

- increased intergranular corrosion resistance, temperature wear resistance, plasticity, impact toughness and serviceability of plates made of oxide-silicon cutting ceramics OKRK-60 by 2.5 times;

- the yield point increases by 1.21 times and the strength and hardness of the plates by 1.05 times;

- improved physical and chemical properties of oxide-silicon carbide cutting ceramics grade OKRK-60 of a new chemical composition in comparison with oxide-carbide RK grade VOK-60, produced by our domestic and foreign industry;

- the resistance of oxide-silicon carbide cutting ceramics grade OKRK-60 of a new chemical composition has been increased, when cutting difficult-to-machine steels 12X18H10T, 40X13, 14X17H2, etc., up to 150 min compared to oxide-carbide RK grade VOK-60, produced by our domestic industry, which is 25-30 minutes, depending on the cutting conditions;

- the temperature regimes of cutting in the processing of difficult-to-machine steels 12X18H10T, 40X13, 14X17H2, etc., as well as thermodynamic laws and modes of this process have been established; the cutting temperature range has been expanded in the cutting zone when processing hard-to-machine "workpiece-tool" steels up to 600 ° C, at which the cutting properties of the tool equipped with cutting ceramics of a new fraction are preserved, while the quality and accuracy of the workpiece does not deteriorate and the cutting edge does not become dull tool;

- rational cutting conditions have been determined, in which the wear resistance of the RI equipped with plates of oxide-silicon carbide cutting ceramics grade OKRK-60 of a new chemical composition, when processing difficult-to-machine, heat-resistant austenitic steels using a new cutting fluids with additives according to the KubGTU patent No. 2101333 with the following mass composition : formic acid 12 ... 13%; maleic acid 8 ... 9%; fumaric acid 7 ... 8%; succinic acid 8 ... 9%; furanones 35 ... 36%, the rest - water, will be maximum.

For experimental verification of the claimed plates made of oxide-silicon carbide cutting ceramics grade OKRK-60 of a new chemical composition, standard samples of plates with dimensions of 10 × 10 × 4.5 mm were made for equipping cutters.

Then the shafts made of difficult-to-machine steel grade 12X18H10T ∅50 were machined to a length of 100 mm with cutters equipped with plates of oxide-silicon carbide cutting ceramics OKRK-60 and cutters equipped with plates of oxide-carbide cutting ceramics of grade VOK-60 based on aluminum oxide.

In this case, the durability of cutters equipped with plates of oxide-silicon carbide cutting ceramics grade OKRK-60 was 140 ... 150 min, and cutters equipped with plates of oxide-carbide cutting ceramics grade VOK-60 based on aluminum oxide was 30 ... 37 min. ... THAT resistance of cutters equipped with plates of oxide-silicon carbide cutting ceramics OKRK-60 was 4.1 times higher than cutters equipped with plates of oxide-carbide cutting ceramics of VOK-60 grade based on aluminum oxide.

This development and manufacture of plates from oxide-silicon carbide cutting ceramics OKRK-60 of a new chemical composition SiO ₂ ≥ 60%, 2%, nitrogen ZrC ≥ 3%; TiC ≥ 30%; WC ≥ 5%; for equipping cutting tools it was introduced at LLC MAPP (Limited Liability Company Mechanization, automation of production processes), when processing shafts made of difficult-to-machine steel 12X18H10T. The use of plates from oxide-silicon carbide cutting ceramics OKRK-60 in the processing of shafts increased the quality and accuracy of the processed parts, which meets the technical and consumer properties of the products. The productivity of the shafts machining has increased, which saved 294 thousand rubles at the MAPP LLC. compared with the use of tungsten carbide RI. Also, plates from oxide-silicon carbide cutting ceramics OKRK-60 were introduced to equip RI, when processing shafts and gears made of difficult-to-cut austenitic steels 12X18H10T, 14X17H2 and gray cast iron SCH18 at the Armavir Machine-Building Plant of the branch of the Open Joint Stock Company "Novozybkovsk Machine Building Plant" Armavir 250 thousand rubles.

Claims (7)

A method of manufacturing a cutting insert from oxide-silicon carbide ceramic, characterized in that silicon dioxide is calcined at a temperature of 1650-1750 ° C, subjected to fine vibration grinding on a vibrating unit for 2.5-3.0 hours and dried, after drying, silicon dioxide is added zirconium carbide, titanium carbide, tungsten carbide and liquid nitrogen in the following ratio: silicon oxide 60%, zirconium carbide 3%, titanium carbide 30%, tungsten carbide 5%, nitrogen 2% and mixing is carried out until the said additives are uniformly distributed over the volume and a suspension is formed, which, after the introduction of binders into it, is subjected to spray drying to obtain a mixture, then a cutting plate is pressed from the resulting mixture, sintering is carried out at a temperature of 3900-3950 ° C and short-term annealing with holding 10.0-15.0 minutes at a temperature of 1600-1650 ° C, and the sintered plate is machined to obtain a roughness of the edges equal to 0.08-0.16 microns.